Docker Interview Questions and Answers

If you’re applying for an DevOps based job, prepare for your job interview ahead of time with these Docker interview questions. Many of these are appropriate Docker Interview Questions and Answers for beginners and experience candidates.

Docker is a containerization platform which packages your application and all its dependencies together in the form of containers so as to ensure that your application works seamlessly in any environment be it development or test or production.

Docker image is the source of Docker container. In other words, Docker images are used to create containers. Images are created with the build command, and they’ll produce a container when started with run. Images are stored in a Docker registry such as registry.hub.docker.com because they can become quite large, images are designed to be composed of layers of other images, allowing a minimal amount of data to be sent when transferring images over the network.

Docker containers are easy to deploy in a cloud. It can get more applications running on the same hardware than other technologies, it makes it easy for developers to quickly create, ready-to-run containerized applications and it makes managing and deploying applications much easier. You can even share containers with your applications.

Docker Hub is a cloud-based registry. We can use Docker Hub to link code repositories. We can even build images and store them in Docker Hub. It also provides links to Docker Cloud to deploy the images to our hosts.

Docker Swarm is native clustering for Docker. It turns a pool of Docker hosts into a single, virtual Docker host. Docker Swarm serves the standard Docker API, any tool that already communicates with a Docker daemon can use Swarm to transparently scale to multiple hosts.

Setting up Development Environment: We can use Docker to set the development environment with the applications on which our code is dependent.

Testing Automation Setup: Docker can also help in creating the Testing Automation setup. We can setup different services and apps with Docker to create the automation testing environment.

Production Deployment: Docker also helps in implementing the Production deployment for an application. We can use it to create the exact environment and process that will be used for doing the production deployment.

Generally, we use Docker on top of a virtual machine to ensure isolation of the application. On a virtual machine, we can get the advantage of security provided by hypervisor. We can implement different security levels on a virtual machine. And Docker can make use of this to run the application at different security levels.

When we build an Image, Docker will process each line in Dockerfile. It will execute the commands on each line in the order that is mentioned in the file. But at each line, before running any command, Docker will check if there is already an existing image in its cache that can be reused rather than creating a new image.

This method of using cache in Docker is called Build cache in Docker.

We can also specify the option –no-cache=true to let Docker know that we do not want to use cache for Images. With this option, Docker will create all new images.

Docker is a very powerful tool. Some of the main benefits of using Docker are as follows:

Utilize Developer Skills: With Docker we maximize the use of Developer skills. With Docker there is less need of build or release engineers. Same Developer can create software and wrap it in one single file.

Standard Application Image: Docker based system allows us to bundle the application software and Operating system files in a single Application Image that can be deployed independently.

Uniform deployment: With Docker we can create one package of our software and deploy it on different platforms seamlessly.